The overall objectives of this project are to elucidate the molecular mechanisms underlying the control of viral gene expression in human cells infected with herpes simplex virus type 1 (HSV-1). This work focuses on four major areas: a) the transcriptional organization of the HSV genome; b) the molecular events involved in HSV mRNA production; c) virus induced synthesis and turn-off of low molecular weight, 4s-7s RNAs and the possible regulatory role of such changes; d) the DNA-dependent RNA polymerase(s) and other transcriptional components involved in HSV transcription. The goals for the current year are the following: 1 Studies on the transcriptional organization of the HSV genome: Analysis of the sensitivity synthesis of early and late viral polypeptides to UV irradiation of the infecting virus to determine minimal sizes of transcriptional units and distances of genes from promoters. 2) Characterize HSV early mRNA, primary transcripts, and transcriptional units: Fractionation and identification of early viral mRNA species; correlation of the identified early mRNAs with the early proteins; and "UV-mapping" of the early viral mRNA species. 3) Investigation of herpes virus induced changes in low molecular weight RNAs: Investigate the previously observed HSV-induced turn-off of host 7S RNA; identify and characterize any new viral encoded 4-5S RNA species by two-dimensional gel electrophoresis and hybridization. 4) In vitro studies on HSV transcription: Development of an in vitro transcription system of isolated nuclei and characterization of HSV-specific RNA produced in this system; studies on RNA polymerases involved in HSV transcription.